1. Technical Field
The present invention relates to a high resolution time-of-flight distance measurement device based on a femtosecond laser, and particularly to a time-of-flight distance measurement device which has a resolution of tens of μm for a distance measurement range of tens of m to hundreds of km.
2. Description of the Related Art
According to the principle used to measure the distance of an object located at a predetermined position using a pulse laser, pulse laser light is radiated onto the object and then the period of time required for the light scattered by the object to return is measured to determine the distance. The instant peak power of such a method of measuring the distance of an object using the pulse laser is higher than that of a method of measuring distance using a continuous wave laser, thus enabling long-distance measurement and achieving a fast rate of measurement.
In the time-of-flight distance measurement using a pulse laser, the period of time between the point in time when, a pulse is emitted from a light source and the point in time at which the pulse is reflected from a target and comes back is measured, thereby determining a distance. The time-of-flight principle is used to measure a three-dimensional shape in huge manufacturing industries including shipbuilding and aircraft industries, and also is variously applied in groundborne or airborne geodetic survey fields which are necessary for civil engineering and construction, and fields related to space development including satellite laser ranging (SLR), laser altimeters, and measuring the distance between satellites.
In recent years, however, in order to increase productivity in huge manufacturing industries such as shipbuilding and aircraft industries, the demand for measurement resolution of ones of mm or less over a measurement range of hundreds of m is increasing, and in the aerospace development field, the satellite constellation industry carried out mainly by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) requires distance measurement between satellites with a resolution of tens μm over a measurement range of hundreds of m. The time-of-flight distance measurement is advantageous because the distance may be measured over a long range of from ones of m to hundreds of km, but the reaction rate of a photodetector for resolving the time interval between pulses has a limitation of tens of ps, undesirably limiting the distance measurement resolution to the level of ones of mm. Hence, this measurement is difficult to utilize in application fields requiring a measurement resolution of ones of mm or less over a long measurement range.